How Often Do Newborn Kittens Poop?

At one week old, a kitten doesnt go to the toilet of it's own accord.  The mother will encourage the kitten to urinate and defecate, by stimulating the kittens bottom when cleaning the kitten.   There wont be any mess for you to  find, as mother cat cleans up after the the kittens at that age. If you're hand-raising the kittens, use a very soft cloth, or cotton ball soaked in warm water and wipe the kittens rear end.  The warm wet feeling will trigger a response from the kitten.  This should be done after every feed. So if you're feeding the kitten 8 times a day, then 8 times a day you will get at least a wee!  Too much information? Sorry LoL

At 3 weeks, your kitten should be still getting all it's food requirements from the mother's milk.  After nursing, the mother licks and cleans the kitten's rear ends.  This stimulates the kitten to pee and poop.  If the mother is not doing this the kittens may become constipated.  You can mimic this action by using a towel or kitchen paper moistened with warm water.  Wipe all around the perianal area and penis.  Build up of faeces in the colon can be toxic.  Stasis in the colon causes more water to be resorbed from the stool and it becomes dryer and more difficult to pass.  If your kitten is not passing anything for over 48 hours you should contact your veterinarian.

A kitten will pee before or after every feeding if you rub the genitals with a warm wet cotton ball. They should poo once every day.

Mother cats will sometime eat the kittens poop.

Constipation in most cases they are constipated because of problems at birth or more likely to of ate something they aren't supposed to.

I have 4 kittens that are about 3 weeks old. They had a bowel movement and it was black.What dose that mean?

We have 4 newborn kittens (riped from mom by dogs) yesterday.  Mother gone babies eating approx.3cc. Every 3 hrs.  They are urinating but have not defecated yet.  When should they?  We are stimulating them.

A lot as they are just tiny and eat to much and have to poop a lot. You did not say how old your kitten was as that would help a lot